In a typical cellular radio system, wireless terminals (also known as mobile stations and/or user equipment units (UEs)) communicate via a radio access network (RAN) to one or more core networks. The wireless terminals can be mobile stations or user equipment units (UE) such as mobile telephones, “cellular” telephones”, and laptops with wireless capability, e.g., mobile termination, and thus can be, for example, portable, pocket, hand-held, computer-included, or car-mounted mobile devices which communicate voice and/or data via radio access network.
The radio access network (RAN) of the cellular radio system covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks is also called “NodeB” or “B node”. A cell is a geographical area where radio coverage is provided by the radio base station equipment at a base station site. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. The base stations communicate over the air interface operating on radio frequencies with the user equipment units (UE) within range of the base stations.
In some versions, particularly earlier versions, of the radio access network, several base stations are typically connected, e.g., by landlines or microwave, to a radio network controller (RNC). The radio network controller, also sometimes termed a base station controller (BSC), supervises and coordinates various activities of the plural base stations connected thereto. The radio network controllers are typically connected to one or more core networks.
The Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the Global System for Mobile Communications (GSM), and is intended to provide improved mobile communication services based on Wideband Code Division Multiple Access (WCDMA) access technology. Universal Terrestrial Radio Access Network (UTRAN) is essentially a radio access network using wideband code division multiple access for user equipment units (UEs). The Third Generation Partnership Project (3GPP) has undertaken to evolve further the UTRAN and GSM based radio access network technologies.
Long Term Evolution (LTE) is a variant of a 3GPP radio access technology wherein the radio base station nodes are connected directly to a core network rather than to radio network controller (RNC) nodes. In general, in LTE the functions of a radio network controller (RNC) node are performed by the radio base station nodes. As such, the radio access network (RAN) of an LTE system has an essentially a “flat” architecture comprising radio base station nodes without reporting to radio network controller (RNC) nodes as opposed to a hierarchical architecture comprising the RNC.
Multi Standard Radio (MSR) Base Station (BS) Overview
A multi-standard radio base station comprises common radio frequency (RF) components, such as power amplifiers, RF filters, and similar, which may be used to operate: More than one radio access technology (RAT); or More than one carrier within the same radio access technology. More specifically the multi-standard radio (MSR) base station is also termed as multi-carrier multi-standard radio (MC-MSR) base station due to the fact that it may comprise a single radio access technology (RAT) with more than one carrier. Hence, single radio access technology (RAT) multi-standard radio (MSR) is a special case of the multi-standard radio (MSR). Furthermore a special case of multi-standard radio (MSR) may also comprise a base station which supports a single carrier within a radio access technology (RAT), i.e., a single carrier single RAT multi-standard radio (MSR) base station.
Multi-carrier multiple RAT (MC-MR) is another term used for the multi-standard radio (MSR). Nonetheless for simplicity and consistency reasons the term multi-standard radio (MSR) is used herein to refer to any base station which has common radio parts to operate one or more carriers, which in turn may belong to the same or different radio access technologies (RATs).
Multi-Standard Radio (MSR) Base Station Scenarios
A multi-standard radio (MSR) base station typically supports either full duplex division (FDD) RATs or time division duplex (TDD) RATs, e.g., all RATs in one multi-standard radio (MSR) are either FDD or TDD. Note that Half Duplex FDD (HD-FDD) is a special case of the FDD. This means HD-FDD, e.g. GSM/Enhanced Data Rates for GSM Evolution (EDGE), belongs to FDD multi-standard radio (MSR) base station. The HD-FDD may also be supported for certain bands for Enhanced (E)-UTRA FDD or for any FDD based technologies.
The technology disclosed herein also applies to the multi-standard radio (MSR) supporting any combination of FDD, HD-FDD and TDD RATs.
Until now the following MSR base stations and their requirements are specified: FDD Scenarios
The FDD scenarios comprise of MSR supporting one or more of the following RATs: Global System for Mobile telecommunications, (GSM)/GSM EDGE Radio Access Network, GERAN, EDGE, UTRA FDD and E-UTRA FDD.
The operating frequency bands specified in 3GPP specification are common for the UTRA FDD and E-UTRA FDD technologies. For example both UTRA FDD and E-UTRA FDD can operate in band 1, e.g. 2.1 GHz. However all UTRA FDD and E-UTRA FDD bands are not specified for the GSM/EDGE operation. Nonetheless some of the GSM/EGDE/GERAN bands are also specified for the UTRA FDD and E-UTRA FDD; examples of such common bands are: UTRA FDD/E-UTRA FDD band 3, e.g. 1800 MHz, and band 8, e.g. 900 MHz.
For simplicity the term GSM is used, which covers also EDGE and other possible GSM evolutions.
Hence the FDD multi-standard radio (MSR) scenarios are classified into the following two frequency band categories:                MSR frequency band category #1 (BC1): Bands supporting FDD MSR for UTRA FDD and E-UTRA FDD operation e.g. bands 1, 10, 13 and similar.        MSR frequency band category #2 (BC2): Bands supporting FDD MSR for GSM, UTRA FDD and E-UTRA FDD operation e.g. bands 2, 3, 5, 8 and similar.        
Even in case of MSR BC#2, in accordance with the operator deployment scenario the MSR BS comprising of the subset of the RATs can be developed. For example a specific MSR BS based on BC#2 may support GSM and UTRA FDD in band 2 in case operator uses only these two RATs.
In future the FDD multi-standard radio (MSR) base station comprising of other FDD technologies may also be introduced. Examples of these scenarios may comprise of any combination of the following FDD/HD-FDD RATs:                E-UTRA FDD and 3GPP2 Code Division Multiple Access (CDMA) technologies, e.g. CDMA2000 1×Radio Transmission Technology (RTT) and High Rate Packet Data (HRPD),        E-UTRA FDD, UTRA FDD and 3GPP2 CDMA technologies, e.g. CDMA2000 1×RTT and HRPD,        E-UTRA FDD, UTRA FDD, GSM and 3GPP2 CDMA technologies, e.g. CDMA2000 and HRPD.        
Similarly the technology disclosed herein also applies to multi-standard radio (MSR) comprising of other technologies, e.g., Worldwide Interoperability for Microwave Access (WiMax), Wireless Local Area Network (WLAN) and their combination with 3GPP and/or 3GPP2 technologies.
TDD Scenarios
The TDD scenarios comprise of MSR supporting one or more of the following RATs: UTRA TDD and E-UTRA TDD.
The operating frequency bands specified in 3GPP specification are generally common for the UTRA TDD and E-UTRA TDD technologies. For example both UTRA TDD and E-UTRA TDD can operate in band 38, e.g. 2.6 GHz.
Hence the TDD MSR scenarios are classified into the following frequency band category:                MSR frequency band category #3 (BC3): Bands supporting TDD MSR for UTRA FTDD and E-UTRA TDD operation, e.g., bands 33, 38, 40, and similar.MSR BS Requirements        
Thanks to the common radio parts, the multi-standard radio (MSR) base station is required to meet the generic radio requirements, which apply for all RATs and for base stations configured for both multi-RAT and single-RAT operation. Example of generic radio requirements are unwanted emissions, spurious emissions, out-of-band blocking, and similar.
In addition there are requirements that apply only to certain MSR base station categories/types. For example some of the requirements may be specific to the single RAT GERAN MSR base station. Similarly modulation quality requirements, e.g., error vector magnitude (EVM)) specific to each RAT needs to be fulfilled by the corresponding RAT.
MSR Base Station Classes
The MSR base station may have the same classes as defined for non-MSR base station, e.g., wide area MSR base station, medium range MSR base station, local area MSR base station, and home MSR base station, for example. Different maximum output power levels are used for different base station classes.
The wide area MSR base station, medium range MSR base station, local area MSR base station and home MSR base station are typically deployed to serve macro cells, micro cells, pico cells and home/office environments respectively. The MSR base station may also be general purpose base station, which is typically used to serve wide range of environment or hybrid environment.
MSR Base Station Classification
The MSR base station may also be classified whether the carriers in a MSR base station using the common radio parts are contiguous or non-contiguous within the MSR bandwidth. Both of them may support different combination of RATs as explained in previous sections.
Contiguous Multi-Standard Radio (MSR)
FIG. 1 shows an example of a distribution of the carriers and RATs in a contiguous MSR base station. The symbols shown in FIG. 1 are defined in section 3 in 3GPP TS 37.104 version 9.3.0 figure 3.2-1. FC, low is a Center frequency of the lowest transmitted/received carrier. FC, high is a center frequency of the highest transmitted/received carrier. Foffset, RAT, low is a frequency offset from FC, low to the lower RF bandwidth edge (FBW,RF,low) for a specific RAT. Foffset, RAT, high is a frequency offset from FC, high to the upper RF bandwidth edge (FBW,RF,high) for a specific RAT. A key characteristic of the contiguous MSR is that all the carriers/RATs are contiguous in frequency domain. It is illustrated in FIG. 1 a frequency block containing 3 contiguous set of carriers/RATs.
Non-Contiguous Multi-Standard Radio (MSR)
The non-contiguous MSR base station is being standardized in 3GPP. FIG. 2 shows an example of the distribution of the carriers and RATs in a non-contiguous MSR (NC-MSR) base station. FIG. 2 shows that the NC-MSR base station comprises of two or more sub-blocks of frequency-containing contiguous carriers/RATs separated by empty slots in frequency domain. Each sub-frequency block consists of contiguous set of carriers, which in turn may belong to the same RAT or different RAT, e.g. a combination of GSM and UTRA/E-UTRA.
In empty slots in the frequency domain another operator may operate. Therefore emissions in the empty slots need to be maintained below the limit as required by the regulatory radio requirements.
The key characteristic of the NC-MSR is that all the carriers/RATs within the overall block of frequency, i.e. the non-contiguous block, share the common radio parts. Hence the generic radio requirements are being defined for all carriers/RATs within the non-contiguous frequency block of NC-MSR.
It should be noted that single RAT BS, e.g., supporting only UTRA FDD or only E-UTRA FDD, may also comprise of non-contiguous carriers. In principle this is a special case of NC-MSR BS, which can also support single RAT scenario in addition to the multi-RAT scenario. For example a single RAT NC-MSR BS may comprise of all non-contiguous block of spectrum belonging to HSPA carriers. In another example a single RAT NC-MSR BS may comprise of all non-contiguous block of spectrum belonging to LTE carriers.
Characteristics of Frequency Bands
A large number of frequency bands have been specified for the MSR nodes, e.g., MSR base station, operation. There may also be large difference between the frequencies of different bands. For instance even in the same region E-UTRA band 1 and E-UTRA band 8 operate in 2 GHz and 900 MHz respectively. Similarly E-UTRA band 2 and band 13 operate in frequency range corresponding to 1900 MHz and 700 MHz respectively in the same region. Another example with significant frequency difference is that of 800 MHz and 3.5 GHz bands, which may also operate in the same region. Secondly the dependency of carrier frequency on the coverage or path loss is well known. The coverage of higher frequency band, e.g., 2 GHz, is worse than that of the lower frequency band e.g., 900 MHz. Furthermore the impact of the transmitter noise to the own receiver is highly dependent upon the duplex gap of the FDD frequency bands. For instance the receiver of the MSR BS operating with FDD frequency bands with smaller duplex gaps is prone to receiving more significant noise or any signals from its own transmitter. Since frequency bands are pre-defined in the standard, hence the corresponding duplex gap is also pre-determined by the MSR node.
Examples of MSR FDD frequency bands with smaller and larger duplex gaps are shown in FIG. 3 and FIG. 4 respectively. In FIG. 3 the duplex gap is 15 MHz and in FIG. 4 the duplex gap is 130 MHz between the uplink and down link frequency bands.
Inter-Modulation (IM) Products in MSR
In general the Inter-Modulation (IM) products occur due to the non-linear characteristics of the devices. For example the IM products are generated when the signal passes through an RF circuitry such as power amplifiers, RF filters, antennas, etc. The Inter-modulation (IM) products are of different orders, e.g., IM2, IM3, IM5, etc. The Inter-modulation (IM) power beyond IM3 is generally very low. Thus for simplicity the IM beyond IM3 are generally ignored. This is further elaborated further below.
Passive Inter-Modulation (PIM) products are of a specific type of IM. The Passive Inter-Modulation (PIM) occurs due to the non-linear nature of the passive RF components in the devices. The Passive Inter-Modulation (PIM) products have traditionally been one of the main concerns in the cellular networks. The Passive Inter-Modulation (PIM) originating from the transmitter (TX) of the device can cause severe noise into the own receiver (RX). This degrades the receiver performance.
In e.g. the GSM networks the Passive Inter-Modulation (PIM) was handled initially with non-duplex equipment. This approach gives an isolation of at least 30 dB between the receiver (RX) and transmitter (TX). For the duplex equipment the Passive Inter-Modulation (PIM) was mitigated with frequency planning and by using frequency hopping which was introduced later.
For broadband systems like UTRA or E-UTRA due to the carriers with low power spectral density (PSD) and limited RF bandwidth (RFBW), the higher order Inter-modulation (IM) did not hit its own receiver band and thus the passive IM did not contribute to any degradation of the receiver sensitivity. The PIM products can be generated from the antenna port of the duplexer in the base station (BS) all the way up to the antennas including connectors, jumper cable, feeder cables, site equipment and antennas as shown in FIG. 5. Some of the mechanisms or sources behind passive IM generation are as following:                Corrosion, Oxides        Dissimilar metals in contact to each other        Magnetic materials in the signal path        Low contact pressure and lower contact area        Debris, pollution and dust at the contact areas        Vibration        Temperature variation        
Intermodulation products occur at frequencies determined by an expression |±mf1±nf2| where f1 and f2 denote the carrier center frequency and the order of Inter-modulation (IM) products is (m+n). The third order IM products, aka IM3, have the highest power level while for higher orders IM, i.e. above IM3, the power level gradually decreases.
One additional aspect for NC-MSR due to multi-RAT operation is that for narrow bandwidth systems, like GSM (GSM carrier BW is 200 KHz), the IM products are also of narrow bandwidth while the IM products from wide bandwidth systems (e.g. HSPA, LTE etc) or combination of wide bandwidth/narrow bandwidth for multi-RAT operation would be of broad bandwidth. This is illustrated in FIG. 6. A rise in noise in frequency domain due to IM is illustrated over frequency band fIM. This is not noticed in the downlink since the DL is of narrow bandwidth.
The Inter-modulation (IM) products are thus dependent upon a number of factors including number of carriers, type of carrier (modulation, amplitude components of carrier, e.g., peak to average, bandwidth, and output power per carrier type etc) and the frequency relation between carriers.
Empirical studies have shown that the level of IM products is higher for non-contiguous cases compared to contiguous scenarios.
Multi-Standard Radio (MSR) Bandwidth (BW)
The MSR bandwidth or more specifically the MSR RF bandwidth (RF) can be determined by taking into account the following factors:                Characteristics of the frequency band        Impact of IM products, e.g., passive IM3, on the own receiver of the MSR node        Output power per carrier type of aggregated output power, e.g., total average power        
The transmission and reception bandwidths are typically same. But they may also be different.
Considering the frequency domain relation for intermodulation generation, the existing paired frequency bands, e.g., band 1, band 7, or similar, may be divided into two categories. In one category the relation between the bandwidth and the duplex gap of the band at the transmitter would never generate IM3 products in its own receiver. In the second category of the frequency bands the own receiver of the base station would suffer sensitivity degradation due to the third order IM (IM3) products. Therefore receiver sensitivity degradation depends upon the size of the declared MSR bandwidth. The MSR RF bandwidth (RFBW) meets the RF bandwidth of the RF components of the MSR node. The examples of RF components are power amplifier, RF filters, receive and transmit antennas, etc.
Table 1 summarizes the IM3 analysis for the paired band, i.e. FDD bands, while table 2 gives the maximum BW which would not cause IM3 in the own receiver for the concerned bands. In other words, Table 2 provides IM3 analysis for existing MSR bands, Paired bands in MSR comprising of E-UTRA, UTRA and GSM/EDGE. There are also few new bands which are being currently standardized, e.g., band 25, which also would suffer from IM3 problem, e.g., receiver degradation.
Table 2 gives specific examples of the MSR BW for frequency bands with narrow duplex gap. Table 2 provides maximum RFBW to avoid IM3 for concerned bands.
TABLE 1IM3 analysis for existing MSR bands, Paired bands in MSR comprisingof E-UTRA, UTRA and GSM/EDGE. Digital Cellular Service is denotedDCS and Personal Communication service is denoted PCS.MSR andDuplexE-UTRAUTRAGSM/EDGEUplink (UL)Downlink (DL)gap size inBandBandBandBS receiveBS transmitrelation tonumbernumberdesignationUE transmitUE receiveband size 1I—1920 MHz-1980 MHz2110 MHz-2170 MHzLarge 2IIPCS 19001850 MHz-1910 MHz1930 MHz-1990 MHzSmall 3IIIDCS 18001710 MHz-1785 MHz1805 MHz-1880 MHzSmall 4IV—1710 MHz-1755 MHz2110 MHz-2155 MHzLarge 5VGSM 850824 MHz-849 MHz869 MHz-894 MHzSmall 6(1)VI—830 MHz-840 MHz875 MHz-885 MHzLarge 7VII—2500 MHz-2570 MHz2620 MHz-2690 MHzSmall 8VIIIE-GSM880 MHz-915 MHz925 MHz-960 MHzSmall 9IX—1749.9 MHz-1784.9 MHz1844.9 MHz-1879.9 MHzLarge10X—1710 MHz-1770 MHz2110 MHz-2170 MHzLarge11XI—1427.9 MHz-1447.9 MHz1475.9 MHz-1495.9 MHzLarge12XII—698 MHz-716 MHz728 MHz-746 MHzSmall13XIII—777 MHz-787 MHz746 MHz-756 MHzLarge14XIV—788 MHz-798 MHz758 MHz-768 MHzLarge15XV—ReservedReserved16XVI—ReservedReserved17——704 MHz-716 MHz734 MHz-746 MHzLarge18——815 MHz-830 MHz860 MHz-875 MHzLarge19XIX—830 MHz-845 MHz875 MHz-890 MHzLarge20XX—832 MHz-862 MHz791 MHz-821 MHzSmall21XXI—1447.9 MHz-1462.9 MHz1495.9 MHz-1510.9 MHzLargeNOTE 1:The band is for UTRA onlyNOTE 2:The band is for E-UTRA only.
TABLE 2Maximum RFBW to avoid IM3 for concerned bandsMaximumMSRUTRAGSM/EDGEUplink (UL)Downlink (DL)RFBWBandBandBandBS receiveBS transmitwithoutnumbernumberdesignationUE transmitUE receiveIM32IIPCS 19001850 MHz-1910 MHz1930 MHz-1990 MHz40MHz3IIIDCS 18001710 MHz-1785 MHz1805 MHz-1880 MHz47.5MHz5VGSM 850824 MHz-849 MHz869 MHz-894 MHz22.5MHz7VII—2500 MHz-2570 MHz2620 MHz-2690 MHz60MHz8VIIIE-GSM880 MHz-915 MHz925 MHz-960 MHz22.5MHz12XII—698 MHz-716 MHz728 MHz-746 MHz15MHz20XX—832 MHz-862 MHz791 MHz-821 MHz20.5MHz
In prior art the admission control or handover decision between network nodes is based on various factors or performance measured such as cell signal strength and/or quality, cell load, user quality of service (QoS) requirement, etc. The radio related challenges of selecting an appropriate carrier belonging to a network node e.g. an MSR base station, and in particular to the NC-MSR base station, have shown that a reduced performance of the communication may be experienced when making a decision based on these various factors.